Which 1933 book was C.S. Lewis’s first published Christian allegory?

The Pilgrim’s Regress was C.S. Lewis’s first published Christian allegory.

Published in 1933, the book follows a character named John as he travels through a landscape shaped by ideas, temptations, and competing philosophies. Its title deliberately echoes John Bunyan’s The Pilgrim’s Progress, but Lewis’s work responds to modern intellectual and cultural debates as well as to older Christian allegorical traditions.

The book appeared soon after Lewis’s return to Christian belief and reflects the concerns of a writer still working out how faith, reason, desire, and imagination fit together. It was not Lewis’s first published book overall: The Pilgrim’s Regress followed earlier poetry and scholarly work. Later Christian works, including Mere Christianity, used more direct nonfiction forms.